What reasons would there be for rehab following a hospital stay not being paid for by Medicare using their “21 days” of rehab coverage?

I've heard from therapists that if the patient is not making progress or refuses to participate in therapy, rehab will/can be discontinued.

I believe for Medicare to cover it it has to be ordered by a doctor caring for that patient and maybe even a doctor covered by Medicare and it has to be a Medicare approved rehab facility. There are a couple of levels of rehab as well and the patient has to meet certain criteria to qualify for the intensive rehab facilities to be covered for instance. The supplemental plan a patient has can come into play here as well. For instance after my mom's stroke her major issue was her speech/aphasia and what she really needed was intensive speech therapy, the hospital coordinator told us we had to get her into an intensive rehab facility quickly while she still qualified (the speech alone doesn't qualify a person, ridiculous!) because that was the only place she would get the intensive speech she needed. We did and she went to a great place where she got speech sessions 2-3 times a day but everything else got so much better so quickly they couldn't keep finding ways to keep her there so she would continue getting the intensive speech, she qualified to be moved to the level down rehab which is really a NH and she wasn't able to be left alone yet (couldn't go home where she lived alone) but that level care while providing the medical care, not leaving her on her own, would only give her basic speech therapy 1-2 times a week and what she really needed was more. Our other option was to take her home, provide care on our own and have her be an "out patient" where she could get the better and more intensive speech therapy so that's what we did. But that was all controlled by Medicare (and her supplement) coverage, if we had had it our way or had the private funds we would have kept her in the intensive rehab facility longer. One other thing to add here since it sounds like you may be at the beginning of a care/rehab adventure, it seemed like things were constantly changing, every-time we thought things were settling down, in place so we could take a breath (I could go home for a bit) we were surprised by a new big change, she settled into rehab...they told us we needed to plan for her leaving in a week, she settled in at home with someone we hired to stay with her when we weren't there (this was a hard one to get her adjusted to)...they decided it was time to do heart surgery so hospital all over again... As you are planning things out try to prepare or consider for the next 2 or 3 steps/possibilities if you can. In some ways I guess the constant transitions made a good distraction, served a purpose but I also think they were particularly hard on my mom (and therefor us) who never dealt well with change but since the stroke has an even harder time with it.

For a person to receive rehab they have to be in a hospital for 3 days. Usually, rehab is recommended to get their strength back. For this the 20 day stay should be enough. Medicare pays as long as the facility shows the person is making progress. If they hit a plateau or not co-operating then they are discharged. But Medicare pays up to that point.

You need to find out their reasoning. Maybe the facility coded the services wrong? Is the rehab billing you? Ask them if they billed Medicare and your supplimental? If a Medicare facility they have to except what Medicare pays them. Like u said, Medicare covers the first 20 days 100% (not 21), 21-100 50%. Supplimental may cover the rest or partial.

Really need more info to help.